In one variety of ink-jet printing cartridges, a foam is used as a reservoir to store the ink and to permit egress of the ink to the printhead on demand for printing.
The foam is typically a polyether-type polyurethane which is reticulated (the cell walls being blown out to provide even flow of ink therethrough) and felted (compressed to 1/3 of its height to increase its density). An example of such a foam is available from Scotfoam (Eddystone, PA) under the trade designation SCOTFELT.
While the foam is ordinarily cleaned by the vendor following cutting to size, it is necessary to determine whether the foam is nevertheless at the proper level of cleanliness for use in the ink cartridge so as not to contaminate the ink and affect its fluid properties.